Topics

Batteries again, Upgrade


Electri-Cal
 

I was yakking with the shop manager at Interstate battery co. yesterday.  Armed with the battery info. from my current two deep cycle power packs, and other data.  Looking for more time at the specificc power amp settings I use for cruise power on Surprise.  How long at what setting, without "drop off" can I expect.  Trying to avoid the switch resetting as trips wear down the battery, and so has more even power through the trip.  Easier on the plates, and faster recharge over average use cycles.

Other part was the weight of each of 4 batteries in the two a--b packs. Going over the series 27 size case added too much on my size boat.  The warehouse manager weighed in on the subject, and we came up with a workable solution for my specific needs.  Electric boats are more iong term drain, but also need constant drain power.  Drop off after say an hour or two can make the battery degrade slightly, if run too low, like over half by much.  Even at that mark, the pulling power requires that I crank up the setting, and that is the problem.  I got a pair of specific batteries, for commercial power drains of a more constant nature. 

Still size 27 case, but with 4.1 extra lb. of lead in each case.  Must be a different composition to hold deep charges even longer.  Not commonly offered from what I see, but I won't know till Charlie and I get on the lake today.  After that run around Dexter, this morning maybe 11 or noonish, we will have the first runs and see how they last.  I expect around 20% longer runs, from what the Interstate manager decided looked about right.  If that works I will add another chapter to this, with model numbers. 

AFTER TESTING A COUPLE TIMES. I would use several opinions as to values and output before I give out data.  That way, if somebody else doesn't get the same results, I'm not  the sole source on this. An added 20% or close, at a reasonable price seems good, but we'll see asap.

Stay Tuned,   Cal                      PS____  Depth finder video camera takes a halt for now !!  I'd rather have more run time on Surprise, this was an option I had not seen before, so here goes !!


  

.


Jove Lachman-Curl
 

Very interesting Cal,
What is the AMP hrs on each of those, four batteries is it? And amp hours total?
Boat size & weight? I'm not familiar with Surprise.
I work at Arcimoto, a small electric vehicle company in Eugene, So I'm always looking at kWh and range etc.
-Jove

On Tue, Aug 25, 2020 at 7:06 AM Electri-Cal <calboats@...> wrote:
I was yakking with the shop manager at Interstate battery co. yesterday.  Armed with the battery info. from my current two deep cycle power packs, and other data.  Looking for more time at the specificc power amp settings I use for cruise power on Surprise.  How long at what setting, without "drop off" can I expect.  Trying to avoid the switch resetting as trips wear down the battery, and so has more even power through the trip.  Easier on the plates, and faster recharge over average use cycles.

Other part was the weight of each of 4 batteries in the two a--b packs. Going over the series 27 size case added too much on my size boat.  The warehouse manager weighed in on the subject, and we came up with a workable solution for my specific needs.  Electric boats are more iong term drain, but also need constant drain power.  Drop off after say an hour or two can make the battery degrade slightly, if run too low, like over half by much.  Even at that mark, the pulling power requires that I crank up the setting, and that is the problem.  I got a pair of specific batteries, for commercial power drains of a more constant nature. 

Still size 27 case, but with 4.1 extra lb. of lead in each case.  Must be a different composition to hold deep charges even longer.  Not commonly offered from what I see, but I won't know till Charlie and I get on the lake today.  After that run around Dexter, this morning maybe 11 or noonish, we will have the first runs and see how they last.  I expect around 20% longer runs, from what the Interstate manager decided looked about right.  If that works I will add another chapter to this, with model numbers. 

AFTER TESTING A COUPLE TIMES. I would use several opinions as to values and output before I give out data.  That way, if somebody else doesn't get the same results, I'm not  the sole source on this. An added 20% or close, at a reasonable price seems good, but we'll see asap.

Stay Tuned,   Cal                      PS____  Depth finder video camera takes a halt for now !!  I'd rather have more run time on Surprise, this was an option I had not seen before, so here goes !!


  

.


Jove Lachman-Curl
 

Also, what it is your operating voltage and motor type.
-Jove

On Tue, Aug 25, 2020 at 11:46 AM Jove Lachman-Curl <jovelc87@...> wrote:
Very interesting Cal,
What is the AMP hrs on each of those, four batteries is it? And amp hours total?
Boat size & weight? I'm not familiar with Surprise.
I work at Arcimoto, a small electric vehicle company in Eugene, So I'm always looking at kWh and range etc.
-Jove

On Tue, Aug 25, 2020 at 7:06 AM Electri-Cal <calboats@...> wrote:
I was yakking with the shop manager at Interstate battery co. yesterday.  Armed with the battery info. from my current two deep cycle power packs, and other data.  Looking for more time at the specificc power amp settings I use for cruise power on Surprise.  How long at what setting, without "drop off" can I expect.  Trying to avoid the switch resetting as trips wear down the battery, and so has more even power through the trip.  Easier on the plates, and faster recharge over average use cycles.

Other part was the weight of each of 4 batteries in the two a--b packs. Going over the series 27 size case added too much on my size boat.  The warehouse manager weighed in on the subject, and we came up with a workable solution for my specific needs.  Electric boats are more iong term drain, but also need constant drain power.  Drop off after say an hour or two can make the battery degrade slightly, if run too low, like over half by much.  Even at that mark, the pulling power requires that I crank up the setting, and that is the problem.  I got a pair of specific batteries, for commercial power drains of a more constant nature. 

Still size 27 case, but with 4.1 extra lb. of lead in each case.  Must be a different composition to hold deep charges even longer.  Not commonly offered from what I see, but I won't know till Charlie and I get on the lake today.  After that run around Dexter, this morning maybe 11 or noonish, we will have the first runs and see how they last.  I expect around 20% longer runs, from what the Interstate manager decided looked about right.  If that works I will add another chapter to this, with model numbers. 

AFTER TESTING A COUPLE TIMES. I would use several opinions as to values and output before I give out data.  That way, if somebody else doesn't get the same results, I'm not  the sole source on this. An added 20% or close, at a reasonable price seems good, but we'll see asap.

Stay Tuned,   Cal                      PS____  Depth finder video camera takes a halt for now !!  I'd rather have more run time on Surprise, this was an option I had not seen before, so here goes !!


  

.


johnacord
 

I have had very good service from the Universal Power Group (UPG) batteries.  I like that they are one of the few battery manufactures that publish ( and make readily available!!) a full range of specs:  AH, KWH & charge discharge curves.   Attached is the data sheet for a 100AH AGM. If I were powering an electric boat using AGM I would consider them a good choice. 

John Acord


 

The batteries Cal got are probably SRM-27s:

https://www.interstatebatteries.com/recreation-vehicles/marine-batteries/deep-cycle

His motors are 24 volt, two 80 lb. thrust Minn Kota trolling motors.

Forgive me if you already know this. Unlike the lithium batteries you use in the Arcimoto, Cal's lead/acid batteries are affected by the Peukert effect. The running times at certain current draws are probably more useful then the usual amp hour ratings for his use. It seems odd to me that they list cold cranking amps for deep cycle batteries. <shrug>

I think he'd be better off using four 6 volt golf cart batteries, rather than two banks of two 12 volt batteries each. Not to mention that golf cart batteries are optimized for running electric motors.

https://www.interstatebatteries.com/recreation-vehicles/golf-cart-batteries

On 8/25/2020 11:46 AM, Jove Lachman-Curl wrote:
Very interesting Cal,
What is the AMP hrs on each of those, four batteries is it? And amp hours total?
Boat size & weight? I'm not familiar with Surprise.
I work at Arcimoto, a small electric vehicle company in Eugene, So I'm always looking at kWh and range etc.

--
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Irreverence is the champion of liberty and its only sure defense. (Mark Twain)
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johnacord
 

John & Clan,

Here you are, from the "Ample Power Primer" :
(looks too big to attach, but for anyone interested I can email it.  Good reading)

Batteries are Purpose Built
The concept of ‘purpose built’ is useful to describe the differences
in battery designs. Just like a hydroplane isn’t the best of cruising
boats, not all batteries are built for cruising.

Starting Battery is Simplest Type
The simplest, and least expensive battery is the starting battery. It
is constructed with many very thin plates. The combined surface
area of the many plates allows high currents to flow through the
battery . . . great for the purpose of starting engines. The starting
battery can’t be deeply discharged without a significant risk of de-
struction. A recent study showed that no starter battery survived
more than 18 deep discharge cycles . . . most survived no more
than 3 deep discharges.

Deep Cycling Requires Thicker Plates
To enable deep discharges, the plates must be made thicker and
the insulating separators made from more expensive materials
than the paper used in starting batteries. Thicker, but fewer plates
means that the battery won’t sustain as high a rate of current, but
will permit deeper discharges without imminent failure. Golf cart
batteries and heavy duty 8D units are thus designed with the pur-
pose of supplying moderate currents for sustained periods. They
aren’t a true deep cycle battery, however, and should be charged
soon after any extensive discharge.

It apparently is possible to build a compromise.  I am using a Lifeline size U1, 33AH "deep cycle", rated at 325 CCA @68 F.  I chose this for a dual purpose starting/house battery with a 50HP outboard.  I rarely discharge deeply with this one so probably OK.  I trust Lifeline, a good solid product.  Not so sure with run of the mill generic companies (I********).  You get what you pay for: the lifeline U1 is a $250 battery!

John A.


Electri-Cal
 


I should have thought that the 20 amp draw was ONE motor !!!  Pushing 40 amps tells me I need to drop my cruise speed below 4 mph. ----  next trip i'll try 3 mph as a reduced speed.  

Yep, better to use the six or eight volt types, if you have room to do that.  The extra weight also adds more weight to push through the water.  After another chat at the Interstate place, and Tuesdays run at Dexter there is a bit more as an opinion.  Charlie and I did the exact same trip as last time, and got pretty much the same results, but some findings were good to know.  I need to go over the wiring again to see if I have the amps reading correctly, later on that part!!   What was just tried was undocking, and redocking, was both motors at higher drain nimbers.  At cruise I can (first) shut one motor off, and the meter drops noticably, but cruise steering is still ok.  I should drop to 3 mph cruise, better time at 15 amps than 20 i've been on.

Next option is I could use both packs as one bigger 24v. source, and have an alarm, or use the depth finder, also the gps to show the charge, they cut out al 11.5v estimated so 23v for the pack.  Then when they stop I would have reserve at reduced power.  OR ----- for longer trips, plug in the third pack !!  My butt gets tired after a couple hours when "riding double" in one position, so adding the "solo 3rd cruising battery pack makes sense for both weight and wiggle room..  If I go alone, I can get way longer runs, as I usually tie up someplace to read, nap, or putter aboard.  At Dexter it's usually run, run, run, and chat and eat, under way, a continual heavier drain than my solo stop and go use

New ones have water caps, I like to monitor that myself. If the acid loses it's potency, Interstat has offered to repair or replace the battery free if that happens !!! The extra 4 lb lead, seems to hold the main amps a bit longer, allow for deeper drain without damage, and hold power a bit longer before drop off.  Not a great big deal, but for a $20. bill each I will do that.  I'd love to do an arc moto battery or similar, but not on my budget,   Thought about a Nissan battery or similar, but also a bunch of $$$,  doing an install and rewire, different battery chargers, some gauges stuff, yet more shop time.  As it is now I can do a good days cruise, go home and recharge for almost zero cost, tows with my Toyota Corolla, at good mileage there !!.

Needs more boating, less fussing over what works now ---- Later,   Cal

.  


Jove Lachman-Curl
 

Ok, I think I understand the system.
2 50lb thrust 24v motors, (are these DC motors? Brushless? etc)
4 (is that right) 12v deep cycle batteries in series for 24 volts. with 2 sets of 2 you can switch between?

One tip that might be helpful is that if you pull the current out of a battery twice as fast you'll only get less than the full capacity you had at the lower discharge rate. I think that's the same idea as the Peukert effect John mentioned. For lithium batteries this is true too, but to a lesser degree.
What it means for design is that you will get more range by running the 2 banks of batteries in parallel at the same time VS running one down, then switching to the other. This halves the current draw on them which reduces losses to internal resistance in the cells. The "reserve tank" idea doesn't really work with batteries in the same way as fuel.

We come across this in our vehicle with regards to design for a lower range lower cost version.... we consider just putting in a dummy cell for one in 3 cells to make a 2/3 capacity pack, but it ends up being closer to 1/2 capacity pack because of the increased losses due to the higher current in each cell.
Hope that's useful.
Are your motors DC? are they controlled by rheostat/potentiometer? or a fancy brushless "DC" electronic motor controller?
Arcimoto vehicles have 2 modules in them. We build them inhouse out of pouch cells and they're 51 volts and ~10kWh each. so the vehicle runs on 102V and 20kWh. Each module is a bit over 100lbs.
These details are just because I've been playing with the idea of trying to get a scrapped module off my boss for an electric cargo bike or boat.
I wonder if you could split 50V to two motors in series for ~24v each, A lot of electric bike parts are 48V also.
Spec on those batteries says 80amp.hrs at 12v, so that's 80x12 = 0.96 kWh per. So one arcimoto module would be equivalent to 11 of those batteries. except would only weight 110lbs vs 550 with lead acid.
Interesting to muse on. Thanks for the chat.
-Jove

On Thu, Aug 27, 2020 at 8:09 AM Electri-Cal <calboats@...> wrote:

I should have thought that the 20 amp draw was ONE motor !!!  Pushing 40 amps tells me I need to drop my cruise speed below 4 mph. ----  next trip i'll try 3 mph as a reduced speed.  

Yep, better to use the six or eight volt types, if you have room to do that.  The extra weight also adds more weight to push through the water.  After another chat at the Interstate place, and Tuesdays run at Dexter there is a bit more as an opinion.  Charlie and I did the exact same trip as last time, and got pretty much the same results, but some findings were good to know.  I need to go over the wiring again to see if I have the amps reading correctly, later on that part!!   What was just tried was undocking, and redocking, was both motors at higher drain nimbers.  At cruise I can (first) shut one motor off, and the meter drops noticably, but cruise steering is still ok.  I should drop to 3 mph cruise, better time at 15 amps than 20 i've been on.

Next option is I could use both packs as one bigger 24v. source, and have an alarm, or use the depth finder, also the gps to show the charge, they cut out al 11.5v estimated so 23v for the pack.  Then when they stop I would have reserve at reduced power.  OR ----- for longer trips, plug in the third pack !!  My butt gets tired after a couple hours when "riding double" in one position, so adding the "solo 3rd cruising battery pack makes sense for both weight and wiggle room..  If I go alone, I can get way longer runs, as I usually tie up someplace to read, nap, or putter aboard.  At Dexter it's usually run, run, run, and chat and eat, under way, a continual heavier drain than my solo stop and go use

New ones have water caps, I like to monitor that myself. If the acid loses it's potency, Interstat has offered to repair or replace the battery free if that happens !!! The extra 4 lb lead, seems to hold the main amps a bit longer, allow for deeper drain without damage, and hold power a bit longer before drop off.  Not a great big deal, but for a $20. bill each I will do that.  I'd love to do an arc moto battery or similar, but not on my budget,   Thought about a Nissan battery or similar, but also a bunch of $$$,  doing an install and rewire, different battery chargers, some gauges stuff, yet more shop time.  As it is now I can do a good days cruise, go home and recharge for almost zero cost, tows with my Toyota Corolla, at good mileage there !!.

Needs more boating, less fussing over what works now ---- Later,   Cal

.  


johnacord
 

Hi Jove,

That is a very nice post, a good explanation of many things that have been discussed.  I tend to be a bit analytical (my physics background slipping in!).  Good work on your part, especially pointing  out the advantage of paralleling to reduce the current drawn from each battery.

John A


 

You'd have been better off if you'd started with four 6 volt golf cart batteries in series, Cal, instead of two banks of two 12 volt batteries. The 6-volters wouldn't have weighed much different, or taken up much more room. Connecting four 6 volt batteries together into one 24 volt bank would have been easier than connecting four 12 volt batteries in series/parallel. Using Interstate's info:

SRM-27 50 lb. 160 min. Reserve Capacity (RC)@25 Amps

GC2-HCL-UTL 58 lb. 383 min. Reserve Capacity (RC)@25 Amps

But you've already invested a lot in twelve volt batteries...

When you've drained your batteries down to 11.5 volts each it's time to stop, not limp home.

If Cal's ammeter is indeed hooked up wrong, and is only measuring the draw from one of his motors, that explains why it seemed like Surprise was WAY underpropped. Doubling the amps shown on his gauge gives figures around what you'd expect from his setup.

You've got a decent setup now, Cal. Work on getting your ammeter sorted out, but go out and enjoy some electric boating. :o)

https://flic.kr/s/aHskZxcaHu

On 8/27/2020 8:08 AM, Electri-Cal wrote:
...
Yep, better to use the six or eight volt types, if you have room to do that.  The extra weight also adds more weight to push through the water.
...
Next option is I could use both packs as one bigger 24v. source, and have an alarm, or use the depth finder, also the gps to show the charge, they cut out al 11.5v estimated so 23v for the pack.  Then when they stop I would have reserve at reduced power.  OR ----- for longer trips, plug in the third pack !!
...
Needs more boating, less fussing over what works now ---- Later,   Cal
--
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Will people ever be wise enough to refuse to follow bad leaders or to take away the freedom of other people? (Eleanor Roosevelt)
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Two 80 lb, thrust 24 volt motors. Using the trolling motor rule of thumb, they ought to draw about 1/2 amp per lb. of thrust. DC. Pulse width modulation speed control. I really don't know if trolling motors are brushed or not...

Mr. Peukert figured out the effect of increased discharge rate on lead/acid battery capacity long ago, and even came up with a "law" to calculate it. It's a rather imperfect law, but useful enough for folks like us:

https://en.wikipedia.org/wiki/Peukert%27s_law

Electric power is nice! :o) I hope you make yourself an electric boat of some sort, Jove. Access to cheap lithium batteries sure gives you a leg up. :o)

Trolling motors are very inefficient at delivering the batteries' power to forward motion. Some of that is due to their propellers being designed to get a heavy bass boat moving, and moving slowly. If possible, it's better to do an inboard installation, or convert a gas outboard. You can use a better motor, and you can fit a proper propeller.

Joe Grez at Electric Paddle has used old sailboat hulls to make his electric launches. The first was a hot-molded Jet 14 that he first turned into a gas outboard runabout, before he started his electric motor business. last year he did the Salish 100 in it, using only solar power:

https://preview.tinyurl.com/y4y24jtl

For this year's Salish 100 he made a new, more comfortable, cruiser out of a fiberglass C-Lark hull. He says he can cruise at 4 knots, with a 50 mile range. (calibrating for boat BS, that's probably 4 knots OR 50 mile range <g>) He didn't tell me what he's using for batteries, but he's got 300 watts of solar panels on a hardtop. I look forward to seeing Joe's new boat in the flesh sometime.

Dan Pence has done quite a bit of cruising in his electric launch, Ginger. First with a bilge full of golf cart batteries, them more recently with lithium batteries. His range with the lead/acid batteries was about 60 miles, and I think he says the range is about the same with the lithiums, but they take up a lot less room and weigh a lot less. You can do quite a bit of cruising on a 50-60 mile range, if yiou can find a marina to recharge every few days.

https://preview.tinyurl.com/y2esxqtd

Myles Twete got his current battery pack from the same place Dan got his -- a defunct electric cae company -- and has an outboard conversion oh his boat, Reach of Tide:

https://flic.kr/p/pwsyc9

https://flic.kr/p/Y5i2v

On 8/27/2020 9:46 AM, Jove wrote:
Ok, I think I understand the system.
2 50lb thrust 24v motors, (are these DC motors? Brushless? etc)
4 (is that right) 12v deep cycle batteries in series for 24 volts. with 2 sets of 2 you can switch between?
One tip that might be helpful is that if you pull the current out of a battery twice as fast you'll only get less than the full capacity you had at the lower discharge rate. I think that's the same idea as the Peukert effect John mentioned. For lithium batteries this is true too, but to a lesser degree.
What it means for design is that you will get more range by running the 2 banks of batteries in parallel at the same time VS running one down, then switching to the other. This halves the current draw on them which reduces losses to internal resistance in the cells. The "reserve tank" idea doesn't really work with batteries in the same way as fuel.
...
Are your motors DC? are they controlled by rheostat/potentiometer? or a fancy brushless "DC" electronic motor controller?
Arcimoto vehicles have 2 modules in them. We build them inhouse out of pouch cells and they're 51 volts and ~10kWh each. so the vehicle runs on 102V and 20kWh. Each module is a bit over 100lbs.
These details are just because I've been playing with the idea of trying to get a scrapped module off my boss for an electric cargo bike or boat.
I wonder if you could split 50V to two motors in series for ~24v each, A lot of electric bike parts are 48V also.
Spec on those batteries says 80amp.hrs at 12v, so that's 80x12 = 0.96 kWh per. So one arcimoto module would be equivalent to 11 of those batteries. except would only weight 110lbs vs 550 with lead acid.
Interesting to muse on. Thanks for the chat.
--
John <@Jkohnen>
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Electri-Cal
 

Whew, lots of input on this.  I looked at 6 volters, but easier wiring, more compact package, space planned for, and cost stopped that.  Pretty happy with what I have, would love more run time and or speed -- not willing to pay the price for that beyond the option I just posted, with 6 batts. if needed for a specific trip.  I couldn't carry Gingers pack size, so that's out.  I remember John and I fried a battery at Fern Ridge, then I needed a rescue tow another round, so not doing only one pack, without a back up. 

I did finish a stern cover, so I have a 4 ft. square deck I could do a solar collector on easy.  The even easier deal is still my Honda 4 stroke with a 10 amp charger back in the stern.  The Honda weighs like ONE size 27 battery , runs a quart of gas about ! charge. Seems like the easiest, fastest to do research on this yet this year.  The little Honda 400 genset is darn quiet,  -- I gotta try that soon as possible as it might solve the problem with my 10 amp charger or the big adjustable one that would do a full pack at once.  I might wish for my 10 amp charger with the Honda genset, sitting back in the stern to be a switchable option that requires no sun, no glass mat batt., and less weight to get the range.  OK, darn it, this happens next week if at all possible, my curiosity just got lit up -- thanks Coots.   Can't use electronics with my genset, older than having filters for that..


Of course I could do all 4 batts. as one pack, tried it once too. Think i'll stick to 27 common battery size, and twin packs, possibly a piggy back, or genset add on.  Unless I find a few thou. $$ laying around for lithiums, easier to consider than write a check for those.  I don't do overnighters anymore, so day trips are way easier on me.

Starting the genset hook up this week end, we'll see !!! ---   Cal


Electri-Cal
 

Friday 6:00 am, rested and looking at stuff I have now.  Lil' Honda (yeah yeah!!) is ready to install now, I had finished an optional bow mount that ties in place.  Add gas and go, if,  (big if !!)  it will handle a decent size charger without stalling. Did that  draw test once, years ago, but a charger or drill, maybe lights at camp, don't recall now.  I hope by next Wednesday, when I meet John at Dexter -- it will be working to some degree.  Also maybe new guage for draw, if I can figure a way to do that without too much grief.  Thats the project, time to roll. Genset puts out 300 watts of 110 v. ---  3 amps of 12 v. ---- will hook charger to 110 side and adjust variable output dial as motor will take.  The whole genset with on board mount weighs exactly 46  pounds, just a few pounds shy of one battery. Wonder what kind of extra muffler I might need to add, since I have run it inside a 30 ft sailboat cockpit, and could still talk, decades ago.

Later,   Cal


Electri-Cal
 

Look lower John, the batts. are the biggest --  listed in the " H " series marine..   Theyr'e even heavier series 27 size, , deeper allowable draw by the extra 4.1 pounds weight. . More expensive components in that type from my take on this.  I just put the original older ones back as a balanced for charging pack, matches better.  Back up pack will be the newer ones, as needed. .

Later,  Cal 


Electri-Cal
 

OOPS, John --- bad Readers ---  they are the M series - as in Mother.... !!  where are my glasses, or other comment.

Later still,  Cal


 

Four 6 volt batteries hooked up in series, a simple on/off battery switch. What's simpler?

The cheapest way to get more range out of the 12 volt batteries you've got is to wire the two battery banks together in series.

On 8/27/2020 10:06 PM, Electri-Cal wrote:
Whew, lots of input on this.  I looked at 6 volters, but easier wiring, more compact package, space planned for, and cost stopped that.  Pretty happy with what I have, would love more run time and or speed -- not willing to pay the price for that beyond the option I just posted, with 6 batts.
...
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The M-27HDC. Four pounds heavier than the SRM-27, same 160 min. rating at 25 amps. About $9 cheaper than the SRM-27. More lead, lower price? Unfortunately, Interstate's specs don't say what's different in their construction... But more lead is Good.

https://www.interstatebatteries.com/recreation-vehicles/marine-batteries/m-line

https://www.interstatebatteries.com/recreation-vehicles/marine-batteries/deep-cycle

On 8/28/2020 9:01 AM, Electri-Cal wrote:
Look lower John, the batts. are the biggest --  listed in the " H " series marine..   Theyr'e even heavier series 27 size, , deeper allowable draw by the extra 4.1 pounds weight. . More expensive components in that type from my take on this.  I just put the original older ones back as a balanced for charging pack, matches better.  Back up pack will be the newer ones, as needed. .
--
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Oops! Of course I meant: "The cheapest way to get more range out of the 12 volt batteries you've
got is to wire the two battery banks together in PARALLEL."
On 8/28/2020 3:07 PM, John Kohnen wrote:
Four 6 volt batteries hooked up in series, a simple on/off battery switch. What's simpler?
The cheapest way to get more range out of the 12 volt batteries you've got is to wire the two battery banks together in series.
On 8/27/2020 10:06 PM, Electri-Cal wrote:
Whew, lots of input on this.  I looked at 6 volters, but easier wiring, more compact package, space planned for, and cost stopped that.  Pretty happy with what I have, would love more run time and or speed -- not willing to pay the price for that beyond the option I just posted, with 6 batts.
> ...
--
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Late in life, Phil Bolger got married. His bride is an engineer, and a German one at that. <g> Together they designed and built an electric launch, Lily. Lily had an easy to build flat-bottom skiff hull designed by Phil, and the power plant was designed by Susanne. Push came from a 24 volt trolling motor, power was from six 12 volt batteries, wired up in a series/parallel arrangement. I can't find the article on Lily -- it must have been in Messing About in Boats -- but I recall that Susanne made quite an effort to isolate the batteries, even using six separate chargers! IIR the article correctly, she was particularly concerned about the batteries hooked together in parallel, using "diodes" (what the Mike O'Brien article in Wooden Boat #137 calls them) between batteries to prevent runaway current from a strong battery to a weak one. Is that really a concern, or was Susanne just overthinking things? To further illustrate her thinking: Lily has a movable battery rack that can be moved fore and aft with a lead screw to adjust the boat's trim for different loads!

The "battery separator" in Lazy Jack charges the small starter battery first, then the larger house battery, but when I start the motor it draws from both, very different, batteries in parallel. <shrug> Nothing has blown up, yet. ;o)

On 8/27/2020 11:36 AM, john a wrote:
That is a very nice post, a good explanation of many things that have been discussed.  I tend to be a bit analytical (my physics background slipping in!).  Good work on your part, especially pointing  out the advantage of paralleling to reduce the current drawn from each battery.
--
John <@Jkohnen>
I cannot help thinking that the people with motor boats miss a great deal. If they would only keep to rowboats or canoes, and use oar or paddle... they would get infinitely more benefit than by having their work done for them by gasoline. (Theodore Roosevelt)
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Randy Torgerson
 

John,


Yes, "runaway current from a strong battery to a weak one" is a real concern.  If one battery shorts a cell then the stronger battery will try to equalize the voltage with a large current resulting.  The large current can melt the interconnecting cables, the terminal and sometimes cause a battery to expand or explode.  Isolating the batteries when charging will lessen the risk.  Also if you are going to parallel batteries make sure they are the same type, manufacturer and date code.  This only only lessens the risk.  Fuse between the batteries can be a life saver.  An ACR (Automatic charge Relay) are now used to change two batteries from the same charge source.  The first  battery is charged and when the voltage reaches a setpoint then the second battery is charged also.  If the second battery's voltage is too low the ACR disconnects and the cycle repeats slowly.


Randy