Deep cycle battery and electric start 8 gpm machine

So, I have decided on purchasing the Honda GX690 engine w/electric start running an 8GPM pump. My question is the feasibilty of using a larger battery for the electric start with dual duty as functioning as the power supply for my 12volt bandit pump. Would the power washer charge the battery? Is this a viable solution? Would the battery that the Honda comes with suffice as a 12v pump supply? Any thoughts or anyone using a similar solution? Thanks in advance.

No get a larger battery for the 12 volt pump and a battery tender. The PW comes with a small battery

Thanks, so the PW would not charge the battery? If I installed a deep cycle larger battery, could I use same battery for starting the PW? Would the PW charge that battery?
Other thought is I have a gas power generator that I could use on the trailer. Would that be a better solution for charging the battery? I want to avoid having to hook up a charger to the trailer.

In theory you could use the larger deep cycle to power the 12v pump, start the PW and have the PW recharge the battery. Here’s the issue: you have to find out what the amp output of the PW alternator/generator is, whatever it is it is probably low. The reason it’s low is that is is only designed to replace the energy needed to start the PW which under normal circumstances is going to be a high draw for a very short period. So it doesn’t need to have much output. What you are going to ask of it is to recharge a deep cycle battery that you are pulling down a significant amount with every use. So let’s say you get a 100 Ahr battery and over the course of the day you discharge it 50%. On the surface you need 50 Ahrs worth of charge to replace it but battery recharging is not even close to 100% efficient so you are going to need a lot more juice for a much longer period of time to get the deep cycle back to 100% SOC. If you leave it even partially discharged for very long the battery will fail prematurely due to PbSO4 accumulation on the plates. This is a long winded way of saying you need to add a battery charger to the trailer or you will find this system will leave you in stranded sooner than later. There is way more to this but hopefully this will give enough information to make a good decision. As an aside I developed and taught the battery maintenance procedures the USMC and most of DOD uses after I retired. Good Luck


understood, thanks for the detailed reply. I am unfamiliar with deep cylce batteries, they probably need more than trickle charge as the starter batteries most likely need. I am trying to build a self sustained trailer (utilizing a 4000watt generator I have sitting in the garage unused for 5 years) where I can have 120/240v AC onboard, untethered so to speak.

Why would you need electricity in a pressure washing trailer? Deep cycle batteries charge on trickle

Inconvenient to hookup charger to trailer, or removing battery to bring to charger each time. No ac in the disconnected garage.

“Why would you need electricity in a pressure washing trailer?” I have a generator wasting away unused and was looking to incorporate if usefull. Could also power air compressors, lights or other stuff, maybe.

It takes about 24 hours top fully charge a deep cycle battery. That’s gonna suck to drive out there every few hours to add gass to generator to charge a battery.

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Answer # 2. See answer #1

They make a pretty cool contraption called an extension cord. LOL, you’re going to spend $20 on fuel to charge a battery with a generator. Payback pretty quick on cord.

The difference between deep cycle and (Starting, Lighting, Ignition) SLI batteries is primarily the thickness of the plates. Deep cycles batteries have fewer but thicker plates that allow it to give up energy at a sustained rate whereas an SLI in the same Group size will have more plates but they are thinner. SLI is better than a deep cycle for the burst required for starting. All that said if I was choosing one to do both jobs I’d go with the deep cycle since the SLI will fail much faster when used for continuous draw.
Any charger will charge either battery type it is just a matter of time. This all works until you get into the charging requirements for flooded cell verses AGM batteries most chargers on the market chronically undercharge AGM batteries because the finishing voltage is not high enough. Sorry this is getting into the weeds. I’ll post a link to one of the classes I used to give…as soon as I find the link.


Thanks MDA1775

I was running with an idea from this guy:

Makes sense to have electricity onboard for a variety of reasons. Just thought I could charge batteries while working other tasks during the job. I also could power tools and other accesories without direct electric hookup. Makes sense to me if you have the room.

Nothing wrong with it if you have a need to run a generator on a regular basis but as was pointed out before it is not at all cost effective as a primary way to charge batteries. A fully discharged deep cycle might take 4-20 hrs to charge depending on battery size and charger output etc. 20 hrs is two tanks of fuel, 4 hrs is 1/2 a tank. You can do the math. Good Luck

By the way if you have a unit that is sitting for 5 years never used you may want to take out the spark plug and spray a little oil in the cylinder and turn it over by hand a couple times to live the walls. May want to take the cover off the bowl of the carb and do the same. Or rather clean it then,lubricate it. You may also want to look in the gas tank for rust it may need to be flushed.