Amp-L-Start in Reverse?

[BobC]

This has nothing to do with my Winnebago but I figured someone here would know the answer.

I've been using an Amp-L-Start for years to charge my chassis battery from my house batteries when they're being charged, either via my converter or solar. It's worked like a charm.

We have a wheelchair lift in our minivan that operates off the minivan's chassis battery. I would like to add an auxiliary (ie. house) battery to operate the lift and have it charged by the chassis battery when the alternator is running. I know there are a variety of solenoids, one-directional and bi-directional devices, etc. that I could use but I have a spare Amp-L-Start and would like to use it if it will work OK. Its 15A output is adequate for my needs since the lift only draws about 6A and only runs for 2 - 3 minutes at a time.

The manufacturer is out of business or I'd ask them.

What do you electrical experts think? Any downsides?

[Morich]

Maybe missing the idea, so some questions?
Is the lift a 12Volt system? If true, do you really need a different battery for the lift?

If the engine is to be running when using the lift, I think the existing alternator and power would be plenty to do the lift. Possibly no extra needed to tie them together as in our RV?

Consider the batteries are only a place to store extra power when we are charging and used when we are not charging. That makes the power from the alternator plenty to operate any reasonable draw for the lift----I think!
Maybe find a point to tie into an exisitng 12V spot, extend a line to where it is needed by first adding a stand alone fuse holder before running the line to the lift?
I tend to like to keep extra lines off the battery itself as the battery tends to make corrosion more a problem than if we move to some point further away from the acid!

But for simple, just tie into the positive battery post with a fuse holder and extend the wire to the lift of a correct size for what the lift needs?
I would guess the lift motro would overload any existing circuits like lights, etc. that might be closer to reach.

But then I've been caught sleeping at times and miss the whole question!!!

[BobC]

That's the way it's hooked up now, but the lift isn't operated when the engine is running. If my wife is on her own, she can't start the car until the chair is stowed and she's already in the car. I just want to add battery power so that, on short trips around town with multiple stops in a relatively short time I don't put too much of a drain on the chassis battery.

This issue is compounded by the fact that the passenger seat is also powered by 12V DC, so it turns, extends out and lowers for easy transfer from her chair. Once in the seat, she operates the lift to stow her chair and then powers the seat to lift her in the vehicle. Once in the vehicle, she moves to the drivers seat and starts the car. The seat is on the passenger side since I drive her most of the time.

I want to run the seat off the auxiliary battery as well. I didn't mention that in my initial post since it seemed to be unnecessary detail, but it does more than double the amp load.

[creativepart]

I don’t know the answer, but why would the amp-l-start care what battery is the “house” and what is the “chassis?” So, I’d guess it would work. Except that the voltage settings for each are built in. The device won’t charge the chassis battery unless the house battery is close to fully charged.

A better idea may be to use a DC2DC charger. You could get an inexpensive one to do this job easily.

[Morich]

Okay! Got more idea of what and why! Yes, sounds like a good idea to have a second battery to avoid running down the start battery and getting stranded.

So the amp-l-start works when we have the ocach charging and want some to slip over to charge the chassis. As I understand it, when coach gets higher than chassis by some set amount it let's this happen.
It seems like if you just reversed the wire to coach and chassis on your setup, current would flow to the chair.
You want the second battery to avoid using too much from start as she moved and finally gets to the driver's seat! Good reason.

My first thought would run to using just a second battery and a manual switch to connect it to start to charge and disconnect when using it as stand alone. That might let the second get a bit higher charge but it also has downsides! One is that it would take training and manual effort to remember to get the switch set right EVERY time used.

Your wife has certainly learned to do a lot of things to get by and might have no trouble getting a new method. But trying to plan things that make life less difficult is good!

Not being on hand and needing cables and larger switch instead of the smaller wires is another.

Since amp-l is on hand, I think it should work but with some points to consider?
The charge current from the amp-l goes over the small wires involved and doesn't top up the second battery quite as high as direct connection might.
If the second battery is too far from the start, is that small wire enough to carry the load?
Part of that will depend on how low the second battery gets when used and what max amount does the amp-l let flow through to the second? I'm not at all up on the amp-l as I only used the trik-l. I think they are just smaller versions of the same idea, but that is pure guess!

I "feel" it would be fine! But is that "feeling" good enough to go on?
You may want to ask a few more questions but then the folks who built the amp-l are out of business, I hear!

Maybe somebody has some specs on limits of the Amp-l? What size wire does it have on it?

[creativepart]

Originally Posted by Morich

You may want to ask a few more questions but then the folks who built the amp-l are out of business, I hear!

Maybe somebody has some specs on limits of the Amp-l? What size wire does it have on it?

It was a one man business here in San Antonio and the owner died suddenly a few years ago with no one to take over the business.

My memory (bad) is that once the house batteries reach 12.6v and the chassis battery is below 12.4v that some charge from the house will go to the chassis.

As to wires mine appear to be 12ga again that’s from my bad memory.

[Morich]

That sounds better if they are 12 gauge! My wires on the Trik-l were more like 16 gauge and that's not good for running across a van for 6-8 feet to recharge a second battery if we got it down a fair amount.
So the big questions might get down to these:
1. How far the batteries are apart, as distance makes the wire need to be bigger to keep
the same level of safe current flow up.
2. How much the second battery is expected to get down to as the lift, etc. are used.
The difference in the voltage of start verus the level of the second is what changes
the amount of current needed to get it back to full charge.

But I would assume the Amp-l start to be built to limit that current flow to what is a safe level for it to operate. Logic says they would not build one that would fry it if you connected a fully discharged start battery to the coach system in the way we would normally use it in an RV!
We are talking of reversing the flow but the same idea, just different names for the two batteries! Instead of charge to the "aux" battery first, we are talking the charge from the alternator going to start and THEN to aux. No big change except in our mind with changing the names?
How much higher, if any, does the alternator voltage go compared to what an RV converter might put out when it is bulk charging a coach battery?
An alternator can run as high as 14 volts at higher revs, but does the converter go nearly that high if the coach battery is way down?

I'm not seeing any obvious problem but that is where it needs some careful thought!
Open to discussion as I have not actually done it like this??

[BobC]

Thanks everyone. Your thinking is the same as mine but I wanted to be sure I wasn't missing something.

1. The existing wiring is 12 gauge and the distance is only about 6' - 8', so that shouldn't be a problem.

2. As far as input amps, I have a PowerMax PM3-55 converter in my MH. The specs show that it's settable for 13.0 - 16.5V max output voltage, so I don't think that 14+ alternator voltage should be a problem. The Amp-L-Start specs/manual is silent on this issue. In any case, the worst that could happen is a burned out Amp-L-Start.

I'm going to give it a try but it's going to be a while since my back is acting up. I'll be sure to update this thread once I do. I may do a test hookup before I install it to see if it works OK.

[Morich]

I feel like it will do okay!
If it's agreeable that you "might" burn out the Ampl-l, then there is not too much worry if the wiring is safe enough and the loss is okay?
I've got a box of stuff that falls in that same group. Too good to throw away but not especially important if I tear it up!
I just tossed a Porter-Cable nailer that really seemed like it was too new to throw out, but the repair estimate was 1/3 to 2/3 of th eprice of a new one, just for parts estimate! Sometimes that box of junk, does turn out to be a box of junk!

After looking really close at repairing it myself, I found the ticket where I bought it in 1998 and it seems like I never used it very much!
The serial number on it is not even in the same realm any more!

[BobC]

Originally Posted by Morich

I just tossed a Porter-Cable nailer that really seemed like it was too new to throw out, but the repair estimate was 1/3 to 2/3 of th eprice of a new one, just for parts estimate! Sometimes that box of junk, does turn out to be a box of junk!

Funny, I have a pneumatic brad nailer that I think I just need to take apart and remove a jammed brad that's been waiting several years for me to do it. I'm not even sure where it is. In the meantime I bought a cordless one, much less of a hassle to use.

[4x4van]

For the OP's issue, I'd just go old (RV) school and install a solenoid between the chassis battery and the Lift battery, activated with the ignition. Cheap, easy, and pretty much foolproof.

[BobC]

Originally Posted by 4x4van

For the OP's issue, I'd just go old (RV) school and install a solenoid between the chassis battery and the Lift battery, activated with the ignition. Cheap, easy, and pretty much foolproof.

I know that's an option, but I have an extra Amp-L-Start. It's also simple to install, no need for an ignition connection.

[Bobn1957]

Originally Posted by BobC

This has nothing to do with my Winnebago but I figured someone here would know the answer.

I've been using an Amp-L-Start for years to charge my chassis battery from my house batteries when they're being charged, either via my converter or solar. It's worked like a charm.

We have a wheelchair lift in our minivan that operates off the minivan's chassis battery. I would like to add an auxiliary (ie. house) battery to operate the lift and have it charged by the chassis battery when the alternator is running. I know there are a variety of solenoids, one-directional and bi-directional devices, etc. that I could use but I have a spare Amp-L-Start and would like to use it if it will work OK. Its 15A output is adequate for my needs since the lift only draws about 6A and only runs for 2 - 3 minutes at a time.

The manufacturer is out of business or I'd ask them.

What do you electrical experts think? Any downsides?

It should work fine!

[BobC]

Originally Posted by Bobn1957

It should work fine!

Thanks, that was my assumption, I just wanted to make sure.