Truth in Battery Specs?

Can you trust manufacturer's battery specs? Or do they "gild the lily" to get more sales?

I've got a 1969 Benelli/Montgomery Wards single cylinder 350cc motorcycle, with 6v electrics, that are barely adequate (more truthful to say barely inadequate). The frame limits the battery size, and the selection of 6v vehicle batteries is already limited. The orig. 1969 battery was an 8 amp-hr battery. I've found two replacements;

1. Yusa 6n11a-1b, a conventional lead-acid battery that I've been using, but has now failed. 11 amp-hr, which is 3 amps over the orig.
https://www.yuasabatteries.com/battery/6n11a-1b/

2. A PowerSonic PS-682F1, a sealed glass-mat battery, of 9 amp-hr.
https://www.mouser.com/ProductDetail/Power-Sonic/PS-682F1?qs=p0FfUnYFXn8QP5vHZZNRdQ==

The Powersonic is a more advanced sealed glass-mat battery, but is only 9 amp vs the 11 amp of the old fashioned lead-acid battery.
Can I trust the published specs (and go w the older higher capacity battery), or are the specs unreliable, and I should go with the "weaker" more advanced battery.

Joe

Your problem is not the battery; it is the output of the alternator/charging system that is inadequate.

There are several different classes of lead-acid battery, depending on the intended application.
eg. the two main ones are:

Car "starter" batteries, which can handle massive currents but cannot stand being discharged much without degrading; typically they are wrecked if fully discharged just a few times.

Deep discharge batteries, such as used for electric buggies, uninterruptible power supplies and "Leisure batteries" in campers and boats.
They can provide reasonable current and stand a lot of charge-discharge cycles.



Looking at the data on the two batteries you mention, the Yuasa 6N11A appears to be a "starter" type battery - it mentions "high cranking current".

The Powersonic one is specified for cyclic or deep-discharge use, so I'd expect that to have a rather longer life in the application you want it for.
(I'm guessing the bike is not electric start - if it is, you must use the Yuasa one and accept the life limitations).

Rjenkinsgb,

Good point, I had forgotten about starting batteries vs deep-discharge. This motorcycle is kick start, w battery points and coil, so a deep discharge style battery is best. Although the deep discharge battery is 9 amp vs the 11 amp starting battery, I agree I'll probably get a better life out of it.

Thanks for looking at this.
Joe

So, does this machine have a "charging system", or do you have to plug it in to an ac-powered charger after riding it?

How is the battery "barely adequate"?
I agree with MIke, in that it would seem you have a charging problem, not a battery problem.

I agree that it's primarily a charging problem, but a better battery is a big help.

Although titled as a 1969, the motorcycle was likely made in 1965. It has a flywheel mounted generator, and a rectifier, providing 6v DC current. Because it's flywheel mounted, the generator turns at engine speed, so at idle the system is consuming more power than it's creating. The battery size is limited by it's position in the frame, and is on the small side. The whole system is marginal, but this was common w motorcycles of that era, although they were soon replaced w better systems when electric starting became the norm.

Improving the charging would entail a complete gutting and replacement w a modern system. Part of the charm of an antique bike is running as much original equipment as possible, so I'd rather try to keep as close to original design as possible. Attached is the wire diagram, and original pages on generator repair.

I'm open to ideas.

Joe

P.S. The blue bike in my signature photo is a 1960's Sears/Gilera, which also had electrical issues steming from the orig design. This board (including you, Crustschow) did outstanding work in designing a 6v AC voltage regulator that turned the bike around in it's performance. It really changed it completely.

The blue Sears/Gilera was in definite need of a voltage regulator (wasn't given one by the factory), so that was an easier fix. The Benelli/Wards bike (photo attached) doesn't have a single obvious problem. The issue is more like a number of weak design flaws, so it's not clear what can be done.

But I'm no electrical guy, which is why I'm reaching out to this board.

So, back to your original question, I think most lead-acid battery ratings are comparable, so you want the highest rated Ah one you can buy.
It would thus appear that the glass-mat battery has a significantly lower capacity than the wet-cell one.
Also the wet-cell type can possibly tolerate overcharging better than a sealed glass-mat.

It might help if you put the battery on a trickle-charger (smart charger) when you are not riding it, so the battery is fully charged at the start of your ride.
I have a charger for my bike that came with a permanent pigtail connection which you connect directly to the battery.
It has a connector at the other end of the wire that the charger plugs into into whenever the bike is sitting.
The connector can be mounted anywhere on the side of you bike where it's out of the way, but readily accessible when you want to plug in the charger

Zapper,
The traditional wet cell battery has 25% more amps, but how about the design? I.e. deep-discharge vs a starter style battery.
If the glass-mat is designed for deep discharge uses, it may be better for the motorcycle (which has a kickstarter) than the traditional wet cell battery, which is probably a "starter" design, calling for a surge of current to start, then remain charged. Take a look at post #3, where this idea was put out.

I agree, trickle charging is a must with this, as the bike's charging system can't be relied on. I might even take a small cell-phone style charger with me, in case I get stranded.
Joe

Don't know about your bike, but is the battery surrounded by the oil tank, like older Harley's? They suffer from short battery life, but it is mainly due to the heat of the oil tank causing the electrolyte to evaporate. How often do you check the fluid level?

Short bus,
Fortunately the battery is clear and should be cool. Look at the picture in post #8, the battery is under the front part of the seat. It looks like there's room for something bigger, but actually the frame rails prevent anything larger. I've also added an air filter instead of the simple trumpet in the photo, and the air cleaner is jammed right up against the battery, taking up room so a larger battery would be hard.
I keep the water topped up, and the battery charged when it's not in use.
Joe

sign216 said:

If the glass-mat is designed for deep discharge uses, it may be better for the motorcycle (which has a kickstarter) than the traditional wet cell battery

Click to expand...

Yes, glass mat batteries apparently are more tolerant of deep discharge than standard wet-cell batteries designed for starting.

What type of battery life are you presently getting?

I got two years from the Yusa standard wet cell. This was abnormally short, and it looks like one cell (of three) shorted out.

The conundrum is that the two characteristics are in opposition. The 9 amp glass mat should have a longer life, but the 11 amp wet cell has 20% more power.

Are battery ratings reliable? Or could Yusa be pumping up their stats to gain sales?

If the Yusa's 11 amps is just advertising "eyewash" then I'll go w the glass mat battery.

sign216 said:

I got two years from the Yusa standard wet cell. This was abnormally short, and it looks like one cell (of three) shorted out.

Click to expand...

I would suggest the crude electrical system is destroying the batteries, it's a VERY harsh environment for a battery.

Nigel,
It's got a Bosch mechanical voltage regulator (see attached). It's possible that the crude circuit is eating batteries. How can I improve it?
Joe

I don't think you can, the basic premise is rubbish to start with, there's not enough power from the generator.

My last bike was a Yamaha DT400 trail bike, and that had crap electrics as well - I was never able to come up with any idea to improve it, converting to 12V would obviously have helped, but it wouldn't improve the power from the alternator.

Is it possible that the mechanical regulator is a drag on the system? It's operation might be crude, and eating up power. A modern regulator could pass on more energy.

sign216 said:

Is it possible that the mechanical regulator is a drag on the system? It's operation might be crude, and eating up power. A modern regulator could pass on more energy.

Click to expand...

It would probably lose a little less, as long as it's well designed, but I doubt it would be enough to solve your issues.

Replacing as many bulbs as possible with LED's would greatly reduce the strain on the electrical system (rear light, brake light, indicators), is the headlight powered by the battery, or direct from the engine?.

sign216 said:

Is it possible that the mechanical regulator is a drag on the system?

Click to expand...

As long as its in good condition it should not be a problem.

However - it's a dynamo system, the dynamo has brushes and a commutator, which wear.

Make sure the brushes are free and plenty of length on them, the com is clean and if there are grooves between com segments, give them a scrape with the tip of a wood toothpick or similar, something that can remove any carbon build-up without damaging the copper.

It looks like replacement brushes are readily available for old 6V bike dynamos.