Increasing ah capacity.

[TriggerGee]

I have an off road mobility vehicle that runs off 2x 12v 73ah gel type batteries in series to deliver 24v to a single 40+ amp motor. Does a great job but uses a lot of power and the original batteries only really have about 27ah usable capacity Question I have is I've got a 12v 100ah deep cycle battery and I'm wondering if I can connect it to the other 12v batteries to increase its range? I'm assuming I'd need two of these batteries in series first then wire them to the "Tramper" in parallel for this to work, is this the case? Thanks for your help

 

[dogman dan]

You can connect two more batteries, as long as you can carry them somehow. As long as it's 24v connected parallel so the result is a larger 24v battery bank, it will be fine.

You might consider and expensive, but better switch to lithium. Though costly, it lasts longer, and gives out closer to the stated capacity than lead.

 

[TriggerGee]

I don't want to buy any extra batteries for it for some time yet as its original ones still have a fair amount of life in them, at least enough for my 10 mile woodland ride. Lithium would be nice but can you imagine the cost of a 24v 70+ Ah lithium pack! Plus I'm not concerned about weight or size, the things huge as it is. Trouble is it uses an awful lot of power to just move as its 150kg so on a smooth flat it uses around 10-15A to travel at 8mph. The batteries in it currently are the original ones from about 7 years ago and it's been used a lot so they've held up pretty well. The bms tells me to charge once I've used 27Ah, my journey usually uses about 20 Ah. In terms of weight and carrying extra that's not a problem as it has a rear rack.

I ask as I've already got this deep cycle 12v 72Ah battery from an electric outboard motor kit that's been sat unused for years and I'd like to put it to use. I know if I had two I could connect them in series to get 24v then connect in parallel to the Trampers 24v's for a greater capacity but is there any way I can use it without buying another one? To fraise it another way, can three 12v 73Ah batteries be connected somehow to give 24v and more Ah or am I being a plonker?

 

[Punx0r]

Yes. Connecting the two original batteries in parallel will give you a 12v 146Ah battery. You can then connect this in series with your third battery. However, capacity will be limited to the weakest link in the chain, so 100Ah nominal. The 46Ah remaining in the two paralleled batteries will be unusable.

Have you checked the 100Ah battery is usable? If it has been sat for years it might be past it.

 

[dnmun]

why did the lead acid battery lose so much capacity? do you charge immediately and keep it charged?

 

[999zip999]

You could look into a desulfation charger. It may help restore life. Always charge lead and always keep fully charged. After they cool down. I read about it but moved to lifepo 4 batteries.

 

[Punx0r]

7 years is quite old for a lead-acid battery

 

[amberwolf]

Lithium would be nice but can you imagine the cost of a 24v 70+ Ah lithium pack!

Except...you don't need a 70Ah pack, with Li. The reason you need such a pack with the lead is that you only get to use a portion of that energy.

Trouble is it uses an awful lot of power to just move as its 150kg so on a smooth flat it uses around 10-15A to travel at 8mph.

I know you give the actual trip info later, but:

So then let's say 30A just to be pessimistic and including slopes or rougher ground.

10 mile trip? 8mph? so let's say 1.5 hours of runtime. So, 45Ah would do it with some to spare, if using a chemistry that allows you to actually get all the power out of it that you put in.

My guess is you need even less than that, but you'd have to measure the actual used Wh to find out, with a wattmeter, on a few of your trips, to get a good average and max.

24V (28V really) @ 45Ah shouldn't be that expensive a pack, depending on what you use for it. Doesn't even need high-C-rate cells, depending on how much power the motors draw on startup and acceleration from a stop and how often you have to do that.

The bms tells me to charge once I've used 27Ah, my journey usually uses about 20 Ah.

So if you assume you need at least 30Ah to account for nonstandard trips and pack aging over time, you still don't need even half of the pack you have now.

That makes it even cheaper than the "guesstimate" I made above would.

To fraise it another way, can three 12v 73Ah batteries be connected somehow to give 24v and more Ah or am I being a plonker?

Not unless your controllers can work on 36V (40+V really), which is unlikely, because you'd ahve to wire tehm all up in series with only three.

Or if your controllers can work on 12V (14V), also unlikely, if you wired them all in parallel.

You can only use more batteries in sets of 24v (28v) in parallel with your existing 24v.

If you have to spend money on another battery anyway, why not just stick it in a piggy bank until there's enough to buy a complete replacement for the aging lead?

(note that the lead is also ballast weight on that vehicle, so if you actually remove it it may tip over on terrain it did not before, so you might have to leave it on there even when using a lithium battery...or, you could carry cargo, tools, etc., down low instead of the lead, if it was enough weight to ballast it).

 

[wesnewell]

Adding another 120lbs is not the answer. Sure it wil work and extend you range, but it also wears out faster, and the increased weight on the vehicle does it no good either. It will wear the tires out faster too. There are lots of better options that won't cost any more in the long run. When you wear out your lead batteries, replace them with a lithium pack. A 40ah lithium pack will give you about the same range as a 100ah lead pack. I'd use 8s rc lipo with ~ $400 cost, but you would probably want a lifepo4 24V pack. You can find them on ebay for $450 and up. Or you can easily build your own using headway 40-100ah cells.

 

[Punx0r]

I'd think a mobility vehicle would require a safe battery with a long life. That's not RC lipo LiFePO4 or NCA LiCO?

 

[dogman dan]

50 ah lifepo4 would be ideal, and you'd get to use at least 45 ah of it.

For sure, adding another 150 pounds won't be helping it get better distance per ah. But stripping off 100 pounds could help the other way.

You might consider adding something more modest right now, which will weigh less than the battery you have. Two new 20 ah cells would add only about 40 pounds, and being new, could provide you with close to 12 ah of usable power. But adding less weight. Cost for that won't be so darn high, possibly close to the same as buying another huge 12v battery.

When it's time to completely replace it, lifepo4 would be great if you can afford it.

 

[jimmyhackers]

you could try refilling the batteries with distilled water.

i know your not supposed to, but thats what the battery makers say so you buy another one.

add about 5ml of distilled water to each cell (6 per battery) let it sit and soak in for about 3 days before you try charging them.

when you do charge put it on a slow (1amp or less) trickle charger with the valve caps off. after a day or so it should be good as new(ish)

reseal and hopefully you will see you amp hour capacity improove.


alsong as the battery hasnt shorted/malfunctioned its more than likely the electrolyte in the cells has dried out. hence a little bit of moisture added back in should help.
ive fixed many an (non fixable/sealed) battery this way.