Does not seem to register power from rechargeable batteries

If your Sam4 ER-390M cash register is displaying a "Warning Power Fail" message, it means that the register has detected a power outage or an interruption in the power supply. Here are some steps you can take to fix this issue:

1. Check the power supply: Ensure that the cash register is properly plugged into a working power outlet. If the power supply is shared with other devices, make sure that they are not causing any power surges or fluctuations.
2. Check the battery backup: The Sam4 ER-390M cash register comes with a built-in battery backup that can keep the machine running in case of a power outage. Check the battery backup to see if it is functioning correctly. If the battery backup is not working, it may need to be replaced.
3. Reset the cash register: Turn off the cash register, unplug it from the power source, and wait for a few minutes. Then, plug it back in and turn it on. This will reset the cash register and may resolve the issue.
4. Contact customer support: If none of the above steps work, you should contact Sam4 customer support for assistance. They can provide further guidance on how to resolve the issue.

It's worth noting that if you experience frequent power outages or power supply fluctuations, it can cause problems with the cash register's electronic components. In such cases, you may need to consider using a voltage stabilizer or a UPS (Uninterruptible Power Supply) to protect your cash register and other electronic equipment.

Not sure about screws but be very careful when changing the battery. If the battery is disconnected, the RAM contents become corrupted and you must perform a RAM clear and re-program it. If it has lost prog already then no problem. If not, make sure you provide an alternate power supply to keep the RAM contents intact.

The first thing to realize is that most wireless keyboards and mice will eat regular alkaline batteries for lunch. This is where most of my clients have gone wrong. It seems they are replacing batteries in a device around every month or even more often. For an office full of wireless devices, this can add up very quickly. Plus it also seems that certain devices act inconsistently with regular alkaline batteries. If you need to purchase a non-rechargeable battery for your wireless devices, you should purchase the "advanced" or "performance" type of batteries such as the Energizer Lithium or Duracell Quantum brands. For what it's worth, the Apple devices usually come with Energizer Lithium brand batteries. However, high performance batteries are more expensive than alkaline batteries and their cost will add up over time. So I don't recommend buying these batteries except in a pinch.
What I really recommend are a particular type of rechargeable battery called low-discharge Nickel Metal Hydride (NiMH). I believe many people stay away from rechargeable batteries because of misconceptions based upon past generations of rechargeable batteries. Many people perceive rechargeable batteries as expensive and prone to failure. But the worst stigma associated with rechargeable batteries are that they don't hold their charge and never seem to be ready when they are needed. The reality is that today's new generation of low-discharge NiHM rechargeable batteries have resolved many of the issues that previous batteries suffered from. Low-discharge NiMH batteries hold their power on the order of months or years after charging. Unlike previous iterations of rechargeable batteries that lost their charge quickly, you can charge these batteries any time and they will be ready for use when you need them.

nothing to do with bartteris the whole system is spoilt just check withg yoiur cannon servicer ...

Most Sharp register, including the ER-A420, have a rechargeable battery mounted inside to hold all memory when the power goes out. It should last a few months, but two years is a bit much. This might get it going:

1. Unplug from AC POWER.
2. Turn the key to PGM.
3. Hold down both paper feed keys (at top-left of keyboard).
4. While holding those two buttons down, plug the power back in.
5. Turn the key back to REG.
6. Enter 1 CASH # to sign on as Cashier 1.
7. Try a sale.

There is a strong chance this won't do the job, because the memory has been randomized by total loss of power when the battery died. Worse yet, the battery may be too far gone to ever take a solid charge again. If so, you probably need the help of a Sharp register dealer to replace the battery, totally clear all memory and reprogram it. It's probably worth the money; the -420 is an excellent little register.

try with new batteries. rechargeable batteries lose their performance in time

Without knowing how long you have been using the mouse it's hard to say. But, my first guess would be that it is time to change the battery. Rechargeable batteries don't last forever.

to register my Garmin Nuvi. I want to get it registered, I tried before I'm not sure how far I got if it is registered or not

your cable might be worn out