Can you start a vehicle while on the charger?

[The motor guy]

I'm talking about a regular gasoline vehicle that uses normal battery to start. Let's say you're battery has been charging for a couple hours and it's holding at 13.5v while on the charger. Any reason why you can't just start it and then let the vehicles alternator take over?

 

[ripcord]

Yes, that's fine. A lot of chargers even have a boost feature that gives a short surge of extra power to help start the vehicle. You want to remove the charger once the car is running, though.

 

[The motor guy]

Yes, that's fine. A lot of chargers even have a boost feature that gives a short surge of extra power to help start the vehicle. You want to remove the charger once the car is running, though.

That was my other question. Say I just want to start it and let it run a bit. Can you still leave the charger on? Mine is just a manual charger, none of that 50 amp boost stuff or anything like that

 

[ripcord]

I would not leave it on. The charger may not have circuitry to prevent problems with being connected while the alternator is running, too. Chances are that the alternator alone can charge the battery as fast it can take it anyway. I put an amp clamp meter on my son's Buick after he ran the battery down and we jumped it and the alternator was putting out 100 amps, so it's likely that keeping the charger on will not do anything beneficial.

 

[The motor guy]

I would not leave it on. The charger may not have circuitry to prevent problems with being connected while the alternator is running, too. Chances are that the alternator alone can charge the battery as fast it can take it anyway. I put an amp clamp meter on my son's Buick after he ran the battery down and we jumped it and the alternator was putting out 100 amps, so it's likely that keeping the charger on will not do anything beneficial.

I need to just get that battery tinder thing and plug it in every so often.

 

[ripcord]

Ah, now I get why you where asking. Yeah, I would disconnect the charger while running the car unless the charger documentation allows it.

 

[The motor guy]

Is a 2 volt rise after connecting the charger a good thing? It was 11.5v before connecting it and I set it to the 6amp setting and it was showing 13.5v immediately after turning it on. I would think if the battery was pooched, it wouldn't raise much

 

[ripcord]

A resting voltage of 11.6 is considered 100% discharged for a flooded lead acid battery. If it's been sitting this way for a long time, the battery is probably pooched. Jumping to 13.5v right away means it likely has developed some internal resistance. It may take a charge and continue to work but it's lifespan is likely effected even if it comes back. Look to see if the voltage goes down again as it charges to know if it is likely to accept a full charge.

Edit: I misstated the voltage for 0% state of charge. It's 10.6v. 11.5v would be about 20% charged, which is still damaging to the battery.

 

[The motor guy]

A resting voltage of 11.6 is considered 100% discharged for a flooded lead acid battery. If it's been sitting this way for a long time, the battery is probably pooched. Jumping to 13.5v right away means it likely has developed some internal resistance. It may take a charge and continue to work but it's lifespan is likely effected even if it comes back. Look to see if the voltage goes down again as it charges to know if it is likely to accept a full charge.

Pretty sure I used it a month ago. Not like it's been dead for 6 months.

 

[Rmay635703]

Is a 2 volt rise after connecting the charger a good thing? It was 11.5v before connecting it and I set it to the 6amp setting and it was showing 13.5v immediately after turning it on. I would think if the battery was pooched, it wouldn't raise much

It’s either a very small battery or it’s sulphated.

Best to let it trickle on an old 2 amp dumb charger overnight.

A desulphator helps and you may be able to partially recover the battery

 

[The motor guy]

It’s either a very small battery or it’s sulphated.

Best to let it trickle on an old 2 amp dumb charger overnight.

A desulphator helps and you may be able to partially recover the battery

It's a small battery. 340 amps I believe. Lawn mower battery basically. Last time I had it on the 2 amp setting and it charged up in like 5hrs

 

[Lubener]

I'm talking about a regular gasoline vehicle that uses normal battery to start. Let's say you're battery has been charging for a couple hours and it's holding at 13.5v while on the charger. Any reason why you can't just start it and then let the vehicles alternator take over?

If the battery is fully charged, I see no reason to leave it in the circuit to crank over your engine.

 

[berniedd]

Once the engine starts, the alternator begins charging the battery so there is no need to keep charging with your charger. Regarding using the charger to boost the 12volts while cranking, unless the charger's literature says it can be connected to the battery while cranking, it is not a good idea for the charger to do so. The sudden large current drain can damage the charger.

 

[zzyzzx]

I did this once on a cold start on my V6 Alero. It was amazing how much faster the car started.

 

[walterjay]

To answer your question...yes. I have done it many times.

 

[demarpaint]

I've done it.

 

[SC Maintenance]

You can. The charger and car voltage regulator should both have over-voltage protection that ensures nothing bad happens.

This of course assumes there both properly working.

Hence I try not to, but if I needed to in order to start something, I would.

 

[cptbarkey]

I take the time to disconnect it. If it cant start by itself on the battery something is wrong.

 

[Snagglefoot]

Yes and I have a charger that will give it a high amperage boast to get it started. But there’s no point to keep it hooked up as an alternator is just that... a battery charger which on my vehicles is at 14.7 V.

 

[oil pan 4]

I'm talking about a regular gasoline vehicle that uses normal battery to start. Let's say you're battery has been charging for a couple hours and it's holding at 13.5v while on the charger. Any reason why you can't just start it and then let the vehicles alternator take over?

I've found that typical car alternator system only give a about 10 to 12 amps with everything else off at idle.
13.5v is bulk charging voltage so the state of charge could really be anywhere when charging at 13.5v.
Better off just letting it sit and cook on the charger.