peter2407
Well-Known Member
I have an Audi estate where the battery is in the spare tyre well in the boot. Assuming I can tie the boat battery down, can I charge it whilst driving using my jump leads? Any tips/concerns/comments?
Can I charge the boat battery while driving my car?
- Thread starter peter2407
- Start date
VicS
Well-Known Member
It will charge ...... in the same way as two batteries in parallel in a bank will charge. ... must be a similar type though!
Safely securing the battery and safely connecting it will be the primary considerations.
Do use proper "battery cable" sized jump leads as it will also be partly supplying the starter current if you stop and restart the car .
It would be sensible also to use special short leads rather than the normal full length jump leads to minimize volts drop.
Beware of poor connections with croc clips. A loose connection that causes a spark could ignite any hydrogen gas given off by the batteries, or one that comes off could short out the whole shooting match.
Maybe some system you could use from the caravanning market where they charge the caravan battery while driving.
However,
More sensble IMHO to charge the battery at home using a decent multistage automatic charger.
Last edited:
peter2407
Well-Known Member
Thanks Vic. Similar type - by which you mean wet cell with wet cell? That might be a problem ....
JumbleDuck
Well-Known Member
I wouldn't even begin to start thinking of driving around with crocodile-clip type jump leads in place.
rotrax
Well-Known Member
I made a simple steel strip holder and a pair of leads adjacent to the battery on my race truck.
On the way to race meetings the bike battery-sometimes batteries with a couple more leads- were fully charged up.
I then started to keep them on the truck over the winter and found they then lasted more than a season. The one on my F1 P&M Kawasaki lasted three years and was still good when I sold it.
Holding them so as to avoid spilling or losing the leads is the tough one.
Good Luck.
On the way to race meetings the bike battery-sometimes batteries with a couple more leads- were fully charged up.
I then started to keep them on the truck over the winter and found they then lasted more than a season. The one on my F1 P&M Kawasaki lasted three years and was still good when I sold it.
Holding them so as to avoid spilling or losing the leads is the tough one.
Good Luck.
VicS
Well-Known Member
Compatible with the car charging system is really what i should have said.
l'escargot
Well-Known Member
Best not do it like this:
pampas
Well-Known Member
fit a split charge relay problem solved, light duty cable runs and no risk of feeding battery to starter.
VicS
Well-Known Member
sailinglegend420
Well-Known Member
Deep cycle boat batteries are not compatible with a car charging system!
Many boats also have car alternators with simple internal regulators often set as low as 13.8 volts. Deep cycle batteries need a multi stage regulator set to their gassing voltage of 14.4 volts or higher otherwise their is a high risk of sulfation. Batteries need to gas slightly to reduce sulfation and to stir up the electrolyte to stop damage due to the acid settling at the bottom of the battery - stratification
So can you use the car to charge the boat battery - yes - but it's not best practice, batteries will die sooner if not charged correctly - but I suspect your boat alternator is the same type with no external multi stage charger added.
William_H
Well-Known Member
I would suggest that a connection to the car system via the cigar lighter outlet might work better. This I think may be disconnected for engine cranking. It is in my car anyway.
If not then plug the battery in after starting the engine. Resistance in the charging wires is the concern you might think. Any resistance in the charge line will reduce the voltage at the battery if a large charge current is possible. (battery low) however the volt drop will reduce the voltage available for charge so current falls so volt drop decreses. It becomes a self limiting arrangement. As the battery charges it can not take the large charge current anyway so nothing lost. Just make sure wires or plug/socket don't get hot and as said make sure the battery is ventilated and restrained.
sailinglegend420 might be right about this not being the best charge practice but it is what we used ever since lead acid batteries and generator charging was invented. The battery will be better off with some charge than none at all.As said it is probably no worse than your usual alternator charging in the boat. good luck olewill
If not then plug the battery in after starting the engine. Resistance in the charging wires is the concern you might think. Any resistance in the charge line will reduce the voltage at the battery if a large charge current is possible. (battery low) however the volt drop will reduce the voltage available for charge so current falls so volt drop decreses. It becomes a self limiting arrangement. As the battery charges it can not take the large charge current anyway so nothing lost. Just make sure wires or plug/socket don't get hot and as said make sure the battery is ventilated and restrained.
sailinglegend420 might be right about this not being the best charge practice but it is what we used ever since lead acid batteries and generator charging was invented. The battery will be better off with some charge than none at all.As said it is probably no worse than your usual alternator charging in the boat. good luck olewill
[2574]
...
Without wishing to be intentionally negative in response I would say that the idea is bonkers. Unlikely to be able to secure the battery well enough and just imagine 20kg of lead/acid coming through the back seats toward you when you braked hard. Buy a nice little Victron multi stage charger and leave it at home.
Uricanejack
Well-Known Member
I have an old camper van. It has a conventional battery for the engine and a deep cycle battery for the house supply. I never use full hook up camp sites preffering
more remote and private spots. The system may be different from a cars but the altenator is the standard one which comes with any GMC van of its age.
works just fine. The deep cycle barttery has its own tie downs.
ghostlymoron
Well-Known Member
I can't see what you gain from this. If you are charging on the way home, why not wait until you get home, then use a mains charger which will charge much faster.
halcyon
Well-Known Member
Déjà vu, got asked this question 40 years ago, back then it was dynamos, blocking diode and volt drop.
Stratification can be a problem, same as leaving batteries on float charge for long periods, but tends not to be a big problem in cars due to the car movement.
Alternator low voltage should not be a big problem, since the 90's 14.2/14.4 volt became a norm, Lucas replacement regulators were set to this so were a cheap simple up-grade for 13.6/8 volt units.
Problems, these day alternators can run at high voltage 15 + is possible, so check voltage of car, split charge isolation should be fitted to stop engine starting from your boat battery, proper rated cables, jump leads NO, if one comes of and meets the other one you have lots of power and no fuse, you need a way to fix the battery in case of accident and insurance.
It is done, that is what I patent in 1973, first portable power pack, people still make them, in fact they make a lot more, why don't you use one of those?
Brian
TSB240
Well-Known Member
I would question how long you can put up with manhandling your battery to and from boat to car etc.
Been there done that.
Assuming you have no choice as no shore power you are much better using solar power to maintain charge.
For the last three years we have used our boat most weekends and do not have the benefit of an inboard with alternator charging our outboard only contributes 6 amps flat out.
We have two 10w flexible panels and a controller that maintains charge and we usually find that the batteries have recovered to full charge between weekends.
Longer boat use we usually get some shore power for our Aldi charger to give them a boost if the sun has not done its job.
Your choice......... I have seen what battery acid does to a car carpet.....
Been there done that.
Assuming you have no choice as no shore power you are much better using solar power to maintain charge.
For the last three years we have used our boat most weekends and do not have the benefit of an inboard with alternator charging our outboard only contributes 6 amps flat out.
We have two 10w flexible panels and a controller that maintains charge and we usually find that the batteries have recovered to full charge between weekends.
Longer boat use we usually get some shore power for our Aldi charger to give them a boost if the sun has not done its job.
Your choice......... I have seen what battery acid does to a car carpet.....
Last edited:
doug748
Well-Known Member
Sounds a very useful idea.
William H has suggested a good plan, you may even have a cigar socket in the boot? I would make up a plug with robust wires, for the job.
William H has suggested a good plan, you may even have a cigar socket in the boot? I would make up a plug with robust wires, for the job.
davidpbo
Well-Known Member
Socket in my boot is permanently powered. Don't know whether it remains connected whilst engine cranks.
glenp
Member
My thoughts on this!
I did exactly the same with a previous camper (which didn't have mains installed) so that if the battery did go flat it was an easy job to recharge it while driving about for the day.
The stipulations I would put are:
Battery in a suitable battery box and well secured in the boot (to stop any possibility of acid spillage and for safety in the event of an accident).
Use a proper split charge relay and suitably sized wiring (easy enough to do - I used a voltage sensing relay like http://www.towsure.com/product/SelfSwitching_Combination_Relay as the alternator connecting type were a problem with the Vauxhall I had).
Do that and it's perfectly safe in my view, although whether there's any real gain over just plugging the battery in when you get home is another matter!
Glen
I did exactly the same with a previous camper (which didn't have mains installed) so that if the battery did go flat it was an easy job to recharge it while driving about for the day.
The stipulations I would put are:
Battery in a suitable battery box and well secured in the boot (to stop any possibility of acid spillage and for safety in the event of an accident).
Use a proper split charge relay and suitably sized wiring (easy enough to do - I used a voltage sensing relay like http://www.towsure.com/product/SelfSwitching_Combination_Relay as the alternator connecting type were a problem with the Vauxhall I had).
Do that and it's perfectly safe in my view, although whether there's any real gain over just plugging the battery in when you get home is another matter!
Glen
pampas
Well-Known Member
VicS
That, or a Lucas type relay (The type that has a very fine winding and min. current draw) The unit on you link looks a nice bit of gear and a lot cheaper than the type I had in mind.
That, or a Lucas type relay (The type that has a very fine winding and min. current draw) The unit on you link looks a nice bit of gear and a lot cheaper than the type I had in mind.
