Question for you EE’s

Strecker25

Strecker25

Well-Known Member
SILVER Sponsor
Nov 20, 2014
4,917
Rochester, NY
Boat Info
2002 410DA
Engines
Caterpillar 350HP 3126
I bought my 4 year old a 24v ATV for his birthday. He loves it and it gets decent range, about an hour at full throttle in the grassy back yard.

the batteries are 2 x 9ah SLA 12v wired in parallel to 24v

my question, if I buy a spare set and want to charge them with a 12v charger is it as simple as wiring them in series to charge at 12v? I suspect yes, since that’s how RV’s and marine chargers work.

On a good rip today…
10A5BF30-FA59-4720-89AD-921537E6A457.jpeg
 
You have it backwards.

Parallel is same voltage but adding current. Series adds voltage but same current.

Easy way to remember it...

ParV or SeriesQ

So to charge on a 12v charger, put the batteries in parallel.
 
douglee25 said:
You have it backwards.

Parallel is same voltage but adding current. Series adds voltage but same current.

Easy way to remember it...

ParV or SeriesQ

So to charge on a 12v charger, put the batteries in parallel.
Click to expand...

Agreed. As long as your charger can support charging multiple batteries in parallel (make sure it has enough max current capability), you can do it that way.
 
Ah no, don't put them in parallel if you want them charged correctly, do one at a time. The charger will try and charge the weaker battery and the stronger one will also charge the weaker one. When new the batteries will be close to equal, but after a few weeks use they won't be. You will get better battery life that way.
 
SKybolt said:
Ah no, don't put them in parallel if you want them charged correctly, do one at a time. The charger will try and charge the weaker battery and the stronger one will also charge the weaker one. When new the batteries will be close to equal, but after a few weeks use they won't be. You will get better battery life that way.
Click to expand...

Except that is exactly how my boat works under normal conditions. SB and port banks. Each bank is two batteries in parallel. The charger charges them as a bank. Not individually. I suspect most boats with battery banks work this way. But I will agree it’s not the perfect ideal for getting max battery life. But I wonder how much more life I would get from my batteries if charged independently. Weeks more? Months? Years? Idk.
 
Thanks all. Charging independently is fine he rides it for a couple hours a day so overnight is plenty to get them on the charger sequentially.

another question since, why not modify a brand new toy?

is 24v=24v in all cases? I ask because I would imagine newer battery technology is far superior to sealed lead acid, specifically lifepo4. At the very least I believe they charge quite fast?

i understand we would need a special charger but how about a 24v lifepo4 or any other battery type that offers more amp hour capacity for even longer runs?

I should leave well enough alone but of course I won’t
 
If higher tech batteries deliver additional performance that you value (like longer utilization during an outing) then yes, get them. If you don’t value that extended life (I don’t need it, for example) then get lower cost batteries. No reason to pay 2x or 3x for a battery if you won’t get 2x or 3x the lifetime out of it …. Unless it delivers other benefits to you like more time on the hook.
 
scooper321 said:
If higher tech batteries deliver additional performance that you value (like longer utilization during an outing) then yes, get them. If you don’t value that extended life (I don’t need it, for example) then get lower cost batteries. No reason to pay 2x or 3x for a battery if you won’t get 2x or 3x the lifetime out of it …. Unless it delivers other benefits to you like more time on the hook.
Click to expand...

well specifically this application is full charge to nearly full discharge (ride on toy with a ~350w 24v motor)

so, I suppose the critical number to look at is the amp hour rating? The stock setup is 2 x 12v sealed lead acid batteries rated at 9ah each
 
scooper321 said:
If higher tech batteries deliver additional performance that you value (like longer utilization during an outing) then yes, get them. If you don’t value that extended life (I don’t need it, for example) then get lower cost batteries. No reason to pay 2x or 3x for a battery if you won’t get 2x or 3x the lifetime out of it …. Unless it delivers other benefits to you like more time on the hook.
Click to expand...
But if the battery lasts 5X longer than the cheaper????
 
Strecker25 said:
well specifically this application is full charge to nearly full discharge (ride on toy with a ~350w 24v motor)

so, I suppose the critical number to look at is the amp hour rating? The stock setup is 2 x 12v sealed lead acid batteries rated at 9ah each
Click to expand...
Let's see - the motor pulls about 15 amps at 24V which is unusually low; regardless let say that you need a nominal 15 amps which means that two 9ah batteries in series will provide 4.5 ah (50% discharge) and will consequently give just 18 minutes of run time. Pretty short.
For fun let's put this in - https://battlebornbatteries.com/product/cyber-monday-50ah-24v-battery/
So now with the lithium battery we have 40ah useable (80%) we get over 2.5 hours or run time until charge is required.
But, it gets better - with larger wiring and more robust throttle control that little motor will wake up as the current delivery capability of the lithium is 10X of the SLA batteries. I suspect though that the little motor's brushes will be smoked in short order.
 
ttmott said:
Let's see - the motor pulls about 15 amps at 24V which is unusually low; regardless let say that you need a nominal 15 amps which means that two 9ah batteries in series will provide 4.5 ah (50% discharge) and will consequently give just 18 minutes of run time. Pretty short.
For fun let's put this in - https://battlebornbatteries.com/product/cyber-monday-50ah-24v-battery/
So now with the lithium battery we have 40ah useable (80%) we get over 2.5 hours or run time until charge is required.
But, it gets better - with larger wiring and more robust throttle control that little motor will wake up as the current delivery capability of the lithium is 10X of the SLA batteries. I suspect though that the little motor's brushes will be smoked in short order.
Click to expand...

I’ll get the motor specs off the tag, I must be wrong in my guess. It does 7-8mph at full throttle for 48 minutes in 3” grass and with my 50# kid on it.
 
scooper321 said:
Except that is exactly how my boat works under normal conditions. SB and port banks. Each bank is two batteries in parallel. The charger charges them as a bank. Not individually. I suspect most boats with battery banks work this way. But I will agree it’s not the perfect ideal for getting max battery life. But I wonder how much more life I would get from my batteries if charged independently. Weeks more? Months? Years? Idk.
Click to expand...

Yep, most boat are wired with batteries in parallel and battery life varies as a result. My boat had two group 31 batteries tied together and I replaced them 7 years ago with single 8D's, one for each engine. Only now am I starting to see signs that I should replace them. Your not going to get 7 years from batteries tied together. So I am guessing years is the answer to your question. And yes there are always exceptions to the norm, so if you or someone you know gets that long from their batteries in parallel then that is the exception.
 
ttmott said:
Let's see - the motor pulls about 15 amps at 24V which is unusually low; regardless let say that you need a nominal 15 amps which means that two 9ah batteries in series will provide 4.5 ah (50% discharge) and will consequently give just 18 minutes of run time. Pretty short.
For fun let's put this in - https://battlebornbatteries.com/product/cyber-monday-50ah-24v-battery/
So now with the lithium battery we have 40ah useable (80%) we get over 2.5 hours or run time until charge is required.
But, it gets better - with larger wiring and more robust throttle control that little motor will wake up as the current delivery capability of the lithium is 10X of the SLA batteries. I suspect though that the little motor's brushes will be smoked in short order.
Click to expand...

heres the little motor spec, so I guess it really is only drawing about 15A. Runs a good 40-50 minutes on a charge though so maybe the speed controller isn’t asking the motor for all 350w? Maybe I’ll put a tach on it, haha
AD5090D3-2656-4209-906B-61AA6964AEF0.jpeg
 
Last edited:
We put a pair of 10Ah LifePo4 12v batteries in it this weekend. It’s like a different machine all together…he didn’t even run out of battery by the time we were done riding.

it’s way faster too, I’m suspecting the motor to crap out sooner than later but they’re cheap..
 
Strecker25 said:
We put a pair of 10Ah LifePo4 12v batteries in it this weekend. It’s like a different machine all together…he didn’t even run out of battery by the time we were done riding.

it’s way faster too, I’m suspecting the motor to crap out sooner than later but they’re cheap..
Click to expand...
We did some modifications to the electric Jeep my twins had 20ish years ago. They still talk about how Dad hopped up their toy. Very cool you are making memories with your son!
 
This is a good application for a lifepo4 battery. You’ll get a slight bump in power, longer runtime and longer life.
 
jmauld said:
This is a good application for a lifepo4 battery. You’ll get a slight bump in power, longer runtime and longer life.
Click to expand...

battery tech is pretty amazing now. I can’t believe how light they are, something like 1.2lbs each. The prices have come way down too
 
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