Charging 12v Battery from 24v supply

[Justme]

With the new info I would recommend using the one bat out of the two in the 24v system for the 12v starter.

Using a starter whilst being a high amp draw of about 300amps it is only for a few second say 10 at most. Thats less than 1 ah used per start. Your looking at less than a 1% imbalance at worse case. You could also remove the alt from the secondary engine & save fuel.

That or change the starter for a 24v one.

 

[the snooper]

so really then whats needed is a solar panel charge regulator with a 24 volt input and a 12 volt output which should do the job BUT

he states that these engines have their own altenator sooooo it would need a simple circuit to disable external charging when the engine is running so as not to over charge

 

[rtbcomp]

With the new info I would recommend using the one bat out of the two in the 24v system for the 12v starter.

Using a starter whilst being a high amp draw of about 300amps it is only for a few second say 10 at most. Thats less than 1 ah used per start. Your looking at less than a 1% imbalance at worse case. You could also remove the alt from the secondary engine & save fuel.

That or change the starter for a 24v one.

Wouldn't multiple starts have an cumulative effect?

 

[rtbcomp]

so really then whats needed is a solar panel charge regulator with a 24 volt input and a 12 volt output which should do the job BUT

he states that these engines have their own altenator sooooo it would need a simple circuit to disable external charging when the engine is running so as not to over charge

Or just get the proper device for the job as Justme says in post #11

 

[eddie49]

In summary: there are two 1-litre-petrol-engined pumps, each one has a 12v starter, alternator, and 19AH battery. One pump gets used predominantly. Sometimes the batteries are found to be flat. It sounds like these two batteries may be old, weak, or under-sized for the job. Perhaps the engines are hard to start, or have a lot of stop/starts.
Anyway, a simple solution may be to just take some heavy cable and link both 12v pump batteries in parallel. That way, they help each other with the starts, and regardless of which engine is running, both batts get charged. I would expect that the alternator on any one engine can cope with charging two batteries in parallel ( i.e. 38AH effectively ). Depending on the distance between the pumps and the price of copper vs. the price of lead, new larger batteries may also be an option.

 

[Justme]

Wouldn't multiple starts have an cumulative effect?

I dont think that the pump engine will be on & off much in a day. Plus each time you start it your replacing the 1ah in no time at all. If its a diesel then there will be very little or even no power used once its running.


You dont need an isolator to turn off the extra charger / PV panel. You can have more than one charge source on the bat. In fact the solar panel will help reduce drag on the pump engine & save fuel.

 

[rtbcomp]

I'm beginning to warm to the idea of new, larger batteries. or even one larger battery serving both pumps?

 

[Delgado]

In summary: there are two 1-litre-petrol-engined pumps, each one has a 12v starter, alternator, and 19AH battery. One pump gets used predominantly. Sometimes the batteries are found to be flat. It sounds like these two batteries may be old, weak, or under-sized for the job. Perhaps the engines are hard to start, or have a lot of stop/starts.

Correct on all counts, although according to the workshop manual (which the manufactures kindly gave me) the batteries that I'm using are the correct size for the job. I'm having a sort out at the moment, replacing any batteries that I deem to be NFG.

Anyway, a simple solution may be to just take some heavy cable and link both 12v pump batteries in parallel. That way, they help each other with the starts, and regardless of which engine is running, both batts get charged. I would expect that the alternator on any one engine can cope with charging two batteries in parallel ( i.e. 38AH effectively ). Depending on the distance between the pumps and the price of copper vs. the price of lead, new larger batteries may also be an option.

Connecting the 2 batteries together in parallel sounds like an interesting idea, as larger batteries are not an option due to the fact that the pumps are a removeable portable unit (they do need to be removed from time to time) and a larger battery wont fit in the compartment so would have to be seperate, taking up space etc.

I dont think that the pump engine will be on & off much in a day. Plus each time you start it your replacing the 1ah in no time at all. If its a diesel then there will be very little or even no power used once its running.

They're petrol driven, and the pumps are normally stop/started multiple times whilst on a job.

I'm beginning to warm to the idea of new, larger batteries. or even one larger battery serving both pumps?

would really like to not have a seperate larger battery if I can get away with it, I'd like them to remain portable as they need to be removed sometimes to set up a pump relay, say If I need to move water a long distance, or to draw water from different supply (i.e; dam, pond, stream,flood etc...)

I saw in another thread that someone recommended solar powered trickle chargers, could this be a viable alternative?

Thanks!

 

[the snooper]

i dont think that you are ever going to find the perfect solution any battery will only provide so many starts if it has low charge times inbetween starts, a bigger battery would help but you say it wouldnt fit
would there be an option to fit some sort of pull start for emergency use.

and can you put us all out of our misery and post some pics and tell us exactly what you use these pums for and why so many starts per day

 

[Justme]

Dribbling info to us on the system has resulted in far to many options.

We still dont really have enough info to give informed advice.

Its looking like you are only having problems as the existing batteries are old & failing. Fit a full set of new bats & then see how things go. Unless you are stopping & starting lots per day with short run times & hard to start engines (need a service?) you should not be having a problem. Check the bats & alts for performance & the service records.

Have they ever worked ok?
How long for?

 

[Delgado]

and can you put us all out of our misery and post some pics and tell us exactly what you use these pumps for and why so many starts per day

Of course, the pumps are used mainly on film sets to supply water for rain, fire fighting, wetting down areas with hoses, wetting down streets with the spray bars that we fit to the back of them, or filling up dams, tanks or IBCs among other things. This means that when the camera is rolling the pumps need to stop (or start), hence the number of stop starts per day.

Dribbling info to us on the system has resulted in far to many options.

We still dont really have enough info to give informed advice.

Its looking like you are only having problems as the existing batteries are old & failing. Fit a full set of new bats & then see how things go. Unless you are stopping & starting lots per day with short run times & hard to start engines (need a service?) you should not be having a problem. Check the bats & alts for performance & the service records.

Have they ever worked ok?
How long for?

My apologies for not giving you all the information at once, being as batteries or engines in general are not something I know much about, it has been hard for me to predict what info is needed to formulate a meaningful answer, and as such I've tried to answer everyone's questions as I go.

So, The pumps are Godiva GP1600's....



They have an electric starter and an auxilery pull start, they are petrol driven, fitted with alternators, have been recently serviced and run well, starting first time when the batteries are good. The battery is not shown in the photo, it is a 12v 19ah motorbike battery, and it sits in the holder in the top right hand corner of the image (above). When I fit new batteries to them they only last a year tops (being recharged when needed), which doesn't seem right to me. Probably doesn't help that the Tankers are stored outside all year round, if we had a depot then I guess it would be a simple case of plugging them in at night as they have a 3 pin socket (like the one in the back of the computer) for either auxilery lights or charging the batteries.

They are fitted on a platform on the back of a water tanker like this, so you can see that space is an issue as I also need to fit hose ramps and other bits and pieces on there too, and there is always the chance of things getting wet ......



Thanks

 

[rtbcomp]

So - the pumps are pull start, not electric start? Petrol engines, so the batteries are used for ignition only?

The engines have alternators (post #33). If the alternators can't replenish the batteries under those conditions then the batteries and/or alternators are probably duff.

 

[Delgado]

Sorry if I wasn't clear, they have an electric start which we normally use, and a pull start for emergencies, have edited my previous post accordingly.

 

[the snooper]

when both pumps are on the truck you could connect a pump to each of the truck batteries in parallel which would make the load even and charge the pump batteries

 

[rtbcomp]

I'm guessing the truck and pumps have a common earth, so you'd have to be VERY careful not to short the "earthy" battery out.

If it were my setup, I'd add a large 12v battery to the truck, charge it with a proper 24-12v charger which switches on when the truck engine is running, or even fit an extra (12v) alternator to the engine.

This 12v battery could be connected to one or both pumps as requiired.

The 12v battery would get charged when the truck is being driven and when one or two pumps are running. I would also add the facility to charge all the batteries from a mains outlet.

 

[Justme]

Check the charging circuits. Sounds like they are not recharging the bats very well (could be over as well as under charging, do you check the electrolyte levels?).

To be honest with the low cost of the bats I would just change them every year. Will be cheaper than any other solution that involves a real person doing real work / spending time on them. You could buy plenty of spares that you keep on float charge ready for swapping out as needed.

Or employ workers that can pull start them then its problem gone.

 

[Delgado]

Ok, thanks for the further advice fellas, I think i'm gonna have to mull it over a bit, work out which way I'm gonna go and how far the funds can stretch. I'll report back and let you know how it turns out.

Thanks everyone for taking the time to post your ideas!

 

[jam670]

Your LPP looks in better condition than the one on our pump! wanna swap?
On the pump we have a 12v charger that works on the charge drop lead in station. It doesn't charge off the pumps 24v.

James