lewiso
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Should I Hook up two 12v gelcells in parallel for car booster box?
Hi -
I've got one of those booster boxes that's used for jump starting cars. It was powered by one large 12V gelcell, now dead and not chargeable. I have two 12V gellcels, each of which is much smaller. A digital VOM reads them at within about .03 volts of one another. I was thinking of connecting them in parallel. Aside from the issue of whether the connectors can handle the amperage, I was trying to think of how this would work out. Any ideas? Thanks.
I've got one of those booster boxes that's used for jump starting cars. It was powered by one large 12V gelcell, now dead and not chargeable. I have two 12V gellcels, each of which is much smaller. A digital VOM reads them at within about .03 volts of one another. I was thinking of connecting them in parallel. Aside from the issue of whether the connectors can handle the amperage, I was trying to think of how this would work out. Any ideas? Thanks.
Callandor
You have to maintain 12v, so hooking them up in parallel will do that. If they can't provide enough amperage to start a car, though, it won't do what is intended.
The total current will be the sum of the current of each battery, btw.
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I doubt the internal resistance of a typical charged gel cell would permit a 10 amp charging current at .1 volt
It can be done but as adam314 said it is not generally recommended for the reasons he gave there. His example may be a bit exagerated, but his recommendation is not.
Hooking gel cells in parallel is mostly okay. But using them to start a car is not a great idea-- these cells are not designed for that huge current draw over a short time period. That's probably why the original one failed.
Just get a regular car battery-- it will be cheaper, provide about 10 times the current,, and will last much longer.
Just get a regular car battery-- it will be cheaper, provide about 10 times the current,, and will last much longer.
ASKER
Thanks for this info -
So from what grg99 says, (which makes sense to me) those booster units that come in a plastic case with cables attached (and i think all use gel cells) are not that great of an idea?
Could it be that there are special gel cells designed for this ? - the original one is a Yaohu 6-FM-17 (YH 12V17Ah.20HR). What is that spec?
One more part of this - there is a rattling sound from this big gel cell when it's shaken. Significant ? It does still have some voltage, but only at low amperage.
Thanks.
So from what grg99 says, (which makes sense to me) those booster units that come in a plastic case with cables attached (and i think all use gel cells) are not that great of an idea?
Could it be that there are special gel cells designed for this ? - the original one is a Yaohu 6-FM-17 (YH 12V17Ah.20HR). What is that spec?
One more part of this - there is a rattling sound from this big gel cell when it's shaken. Significant ? It does still have some voltage, but only at low amperage.
Thanks.
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gel cells have a higher internal resistance than your typical car battery.
A typical gel cell will be in the range of 10 to 30 milliohms
A typical car battery will be in the range of 2 to 4 milliohms.
So in a tug of war the gel cell loses, big time. Only about 10% of the power is going to flow into the car battery, the other 90% will be dissipated in the gel cell.
The only good news is if the car battery is completely discharged, it's likely to go quite a bit up in resistance, so it will not drag down the gel cell so much.
A typical gel cell will be in the range of 10 to 30 milliohms
A typical car battery will be in the range of 2 to 4 milliohms.
So in a tug of war the gel cell loses, big time. Only about 10% of the power is going to flow into the car battery, the other 90% will be dissipated in the gel cell.
The only good news is if the car battery is completely discharged, it's likely to go quite a bit up in resistance, so it will not drag down the gel cell so much.
Adam314 answered the question asked. I added a very little bit. grg99 added some specific info and d-glitch decoded a model number correctly
I think the fact that they don't provide enough current is the answer to why it's not a good idea.