# Increase range by putting batts in parallel?

Hi all,
I’m totally new with the whole EV idea. I did some research a while back and now that gas is going back up I’m back on the idea of maybe converting a junker over to electric.

I’ve been looking at motors, kits, batteries and such so I’m somewhat aware of what all this is going to cost. My main concern, which I’m hoping to get some of your help with, is range. I need about 70 to 75 miles round trip each day for my work commute. I can go two different ways to work - highway or back roads. The highway I would need to achieve 75mph. The back roads I would need about 55 to 60mph.

My question is would I be able to put 12 pairs of 12v batteries (2 batteries in parallel connected in series with the other pairs)? Does this extend the range from the usual/about 50 miles to roughly double that? Does it work that way…can you put some in parallel like that? Seems like it would work since the voltage would stay the same, but the amperage would double.

Anyways, that’s what I’ve got in mind. Can somebody tell me if it would work that way or not, and why? I’m eyeballing a broken Geo Prism for \$500.

[QUOTE=courtney2018;2751]Hi all,
I’m totally new with the whole EV idea. I did some research a while back and now that gas is going back up I’m back on the idea of maybe converting a junker over to electric.

I’ve been looking at motors, kits, batteries and such so I’m somewhat aware of what all this is going to cost. My main concern, which I’m hoping to get some of your help with, is range. I need about 70 to 75 miles round trip each day for my work commute. I can go two different ways to work - highway or back roads. The highway I would need to achieve 75mph. The back roads I would need about 55 to 60mph.

My question is would I be able to put 12 pairs of 12v batteries (2 batteries in parallel connected in series with the other pairs)? Does this extend the range from the usual/about 50 miles to roughly double that? Does it work that way…can you put some in parallel like that? Seems like it would work since the voltage would stay the same, but the amperage would double.

Anyways, that’s what I’ve got in mind. Can somebody tell me if it would work that way or not, and why? I’m eyeballing a broken Geo Prism for \$500.

Yes it’ll work…but it’ll be expensive, heavy, and place taking. You’ll need 24 deep cycle battery (usually around 250usd) 12v 90ish Ah. So a total of 6,000usd all that is going to weight 750lbs(about).

Maybe if you strip(remove back seat…) your Geo you’ll get enough space.

Thanks!

I was considering doing a massive stripping of the interior for weight and better aero. What I’m considering doing is taking everything out of the inside. Extend the trunk into the cabin. The passenger seat would be removed for cargo space. I’d replace the dash with a simple sheet metal box as wide as the car. It would somewhat resemble the inside of a racecar. That’s the level of simplicity I was thinking of for the inside.

I don’t know how much weight removed that adds up to, but I’m guessing that with all that removed and the addition of the batteries I might be close to what the car weighed to begin with.

So what I’m proposing, with the parallel battery set up, you think I can effectively “double” my range? Maybe not exactly double, but definitely get the range I need?

What style batteries are most people going with? I’ve read plus and minuses about all of them. I was considering the deep cycle sealed batteries.

Thanks again!

There are a couple of things you need to consider about putting the batteries in a passenger compartment. #1 Gas, when charging the batteries make hydrogen gas which is highly flammable, you remember seeing the Hindenberg burning in old newsreels? it had Hydrogen gas to float it in the air, shortly after that they went to Helium. Any spark could cause a fire or explosion from the gas. Power Venting is a necessary step to keep yourself safe. #2 Restrant, restraining the batteries is a must in case of a accident or sudden braking. A 80 lb battery could be deadly for you or a passenger. Not to mention the battery acid is very potent. #3 High Voltage, you would have to put in a barrier inbetween the front seat and rear so no one would accidently touch the connections which would be HIGH VOLTAGE DC. Theese are just a few reasons that you shouldn’t put the batteries in the passenger compartment.
SAFETY FIRST

Thanks, but I wasn’t thinking of putting batteries in the cabin. I would extend the trunk space up to the drivers seat (wthin about 12" or so). It would be sectioned off from the cabin and sealed so there isn’t any air exchange between the trunk and the cabin.

And I was considering using the sealed lead batteries. I was thinking those wouldn’t emit any gas. Do they still emit hydrogen when charging even if they’re a “sealed” battery?

Thanks!

So, I’m fairly new here, too, so straighten me out if what I’ve read doesn’t jive.

Isn’t this application exactly the type of thing one would use 6v batteries for instead?
From what I’ve seen, you get the same voltage level, but they’d all be in series,
and you’d be using the batteries designed for this purpose. (???)

[QUOTE=courtney2018;2765]Thanks, but I wasn’t thinking of putting batteries in the cabin. I would extend the trunk space up to the drivers seat (wthin about 12" or so). It would be sectioned off from the cabin and sealed so there isn’t any air exchange between the trunk and the cabin.

And I was considering using the sealed lead batteries. I was thinking those wouldn’t emit any gas. Do they still emit hydrogen when charging even if they’re a “sealed” battery?

Thanks![/QUOTE]

Have you done the math the see if there is enough space? Because on my future car I calculated that I could only put 10 batteries(best option), but I’ll only put 8 (96V)

[QUOTE=SilvaDragon;2766]So, I’m fairly new here, too, so straighten me out if what I’ve read doesn’t jive.

Isn’t this application exactly the type of thing one would use 6v batteries for instead?
From what I’ve seen, you get the same voltage level, but they’d all be in series,
and you’d be using the batteries designed for this purpose. (???)[/QUOTE]

12V 100Ah battery

2 of them in parallel = 12V 200Ah More energy available
12 of them in series = 144V 100Ah More voltage available

So two packs of 12 batteries will do 144V 200Ah

Voltage is like the size of a hose, and the Ah is the size of the tank of water.

I used this article to size what batteries I’ll need. Tell me if your experience tells you different. Looks like I’ll have to get batteries in the 200+Ah range. Probably around 250 or so. This article puts in some safety factors, but I’m curious if others here have experienced great performance out of their batteries with less that what is described in this article.

That’s a good way of looking at it.

Courtney
A rule of thumb figure that I have seen is 1 mile of travel for 20 pounds of lead acid batteries. This obviously varies with speed, vehicle type and other factors but in my case (Mitsubishi pickup) it has proven out. One thing that you don’t hear much about is temperature: a lead acid battery loses about half @ 20 degrees. A while back I made what should have been an easy trip except that it was chilly and by the time I got home I was down to 20 volts and 9 1/2 mph. Depending on where you live that may be a consideration.
Good Luck
tommyt

I’m in south Florida. In the winter the temperature during the day can get in the 50’s (deg. F), but typically it’s warm just about all year round.

Hi all,

You’ve got to be careful about adding too much weight. At a certain point, the extra batteries you add to increase the range end up adding more weight to the car and ultimately decrease the total range. Plus, you can make the car unsafe by exceeding the Gross Vehicle Weight Rating (GVWR) by a lot. Little cars are not designed to carry a lot of weight to begin with. Probably why small pickups are popular candidates for conversion…

Doesn’t sound like your requirements are all that crazy…a 50 mile range sounds completely do-able. Good luck!

From what I have learned getting bigger batteries is better than putting them in parallel. if you put two batteries in parallel and 1 is bad the good wil discharge through the bad one unless they are isolated, which complicates battery wiring.